Tamara Starkova knew that something was wrong before her husband did because of a book she had read, Two Captains, by Benjamin Kaverin. It is the novel upon which the hit Russian musical Nord-Ost is based, the story of a mute orphan who, with Soviet-era invincibility, overcomes two wars, the siege of Leningrad and a polar expedition to win the heart of a beautiful woman.

To those in the theatre that night who hadn't read the book, among them Starkova's husband, Sasha, and her 16-year-old daughter, Natasha, it seemed in keeping with the plot when, a way into the second act, a man ran on stage waving a gun. Only Tamara Starkova stiffened. There were soldiers in the book, but at this point in the story they should have been German. The man on stage was in a uniform that looked, to Starkova, suspiciously unlike the period fatigues of the Third Reich.

Seven months later, the 42-year-old paediatrician is in a gloomy hotel room in London twisting a tissue round her fingers. Natasha and Sasha are both dead. On the advice of her state-provided grief counsellor she has decided not to get angry, neither with the Russian government nor the Chechen terrorists nor, she says, with God. She has been advised to cope by telling herself that something terrible would have happened anyway, that this was her fate. But despite her best efforts, when Starkova relates the story of her family's death, it is with a self-possession so fierce that it would seem, at some level, to draw on the concentrating power of fury. "It's been very difficult," she says, through her translator, Tom, whose voice gets lower the further into the story we get. "My son has helped me a lot, like a ray of light in a very dark kingdom. I've tried hard to find things to do, learning to drive, drawing, reading, trying hard to fill my life."

Her black eyes rage; the tissue goes round.

One hundred and twenty people died in the Moscow theatre siege last October, two of them at the hands of the terrorists, the rest accidentally killed by nerve gas used by Russian special forces to subdue (in the event, kill) the Chechen rebels. Some of the survivors are suing the government over the rescue effort but Starkova is not one of them.

If Sasha and Natasha had died in a car crash, she says, she might have reacted differently. "I might have wanted to commit suicide. But because I was in the theatre, because I lived through death, I felt that in a sense I had been reborn. I look at life, at things and people, with different eyes."

During the siege she was shot in the stomach. "Understanding death has helped." The Starkovas didn't often go out as a family. Since childhood, Natasha had suffered from high blood pressure and was what, in another era, might have been called "delicate". She liked dancing, drawing and sewing. Her brother Sergei, 11, didn't think a musical about a mute orphan sounded like much of a night out and decided not to go. He stayed at his aunt's house that night.

When the gunman appeared on stage that night, Starkova turned to her husband, a police officer, and whispered, "What's going on?" Sasha teased her for being a wimp. When the man fired shots into the air, he reassured his wife that this was what modern theatre was all about. When the man cracked his rifle butt against a member of the cast's head, Starkova said, "What's going on?", and this time Sasha hesitated. The theatre went quiet as audience members struggled to make sense of what they were seeing. Eventually Sasha said to his wife: "Terrorists."

The man on stage explained that he and his 50 associates were holding the 800 audience members to ransom for an end to Russian hostility in Chechnya. "There was no panic," says Starkova. "They used psychological methods to wear us down. They shot above our heads. They ordered us to stand or lie down and said, 'Are you prepared to die? We're going to blow the place up'."

During the first night of capture, Starkova tried to distract her daughter by reminiscing about family history. She fished out some paper and got her to draw. When the gunmen fired into the ceiling, Starkova and her husband covered their daughter's body with their own. "Sasha spent a lot of the time with his head down between his knees. I would ask him, are you OK? And he said he was fine. It was worst of all for him because he felt that as head of the family he should defend us. Most of the men were like that, apathetic. They didn't know what to do. There was nothing they could do."

By the second day, after several captives had escaped through the toilet window, the audience was forced to use the orchestra pit as a communal latrine. The captors threw chocolate and chewing gum into the crowd "as if we were dogs", says Starkova. "I forbade my daughter from reaching for them. I said, 'Don't degrade yourself. If one lands in your lap, fine, but otherwise leave it.'"

The second night, when she slept, Starkova dreamed that she was back at work, relating to everyone her experience in the theatre. She and Natasha decided that on the strength of the dream they were going to survive, and when the gunmen said they could use their mobile phones, Starkova felt sufficiently optimistic - she laughs as she says this - to put in a call to her office. "I told them I wouldn't be coming in, I was in the theatre siege." Tom laughs too. "And they said, 'How on earth did you get in there?' And I said, 'I bought a ticket!'" Who else did she ring? She stops laughing. "I rang my sister. I told her where to find money set aside for the funerals."

While audience members were calling their loved ones, Joseph Kobzon, a negotiator, was trying to reason with their captors. "You've still got children to father, girls to love," he pleaded with one of the gunmen, who replied, "No, we're suicide bombers. We want to die more than you want to live."

"My abiding memory of the Chechen men is of them running around shouting," says Starkova. "But the Chechen women would say "please" when they asked for something. I related in some small way to the women. There was one who said she had lost her husband and child, and maybe any mother in that position would be capable of taking this step."

By the third day, Starkova and her husband had stopped shielding Natasha when the gunmen fired. Their despair was total. They had had almost nothing to eat or drink. "Such an apathy came over us. We didn't care if we lived or died. They could blow us up, whatever. By that stage we weren't afraid of anything. We were very low."

It was at this point that one of the hostages lost his head and started running around hysterically. Lest the whole theatre go up, Sasha rugby-tackled him to the ground and in the ensuing scuffle, Starkova was shot in the stomach. The injury would save her life but at the time, she thought it likely she would die and was only thankful that it gave her a chance to get Natasha out. As the Chechens prepared to evacuate her, she asked if her daughter could go too; they said yes. Then, at the door of the theatre, they changed their minds. Starkova's last memory of her daughter is of her back, retreating into the theatre, and then of her own hysterics. "I have to stop myself from replaying that moment, or else I won't have the strength to carry on."

For one and a half days Starkova lay unconscious in hospital and when she came round, the first question she asked was, "Did they blow up the theatre?" The nurse told her no and advised her not to speak until she was stronger; she should write down any further questions. On a piece of paper, Starkova asked first if her daughter was alive, and then about her husband. She received in each case a negative reply. Both had been killed by the nerve gas pumped into the theatre. "It is their job," she says, helplessly, of the special forces and lapses into silence.

Before she returned home, local businesses offered to radically change the interior of Starkova's flat, to lesson the pain of association. But in the end, she decided to keep it as it was. "I was very frightened of returning from hospital. But when my son opened the door, I felt that the darkness had evaporated, and I didn't even cry. In the flat, there was a lightness. The place had such happy memories of being together. We put up the wallpaper together, my husband and I."

She is still on sick leave, but will return to work and take up a promotion, as head of department in a medical practice in the northwest borough of Moscow. "I am growing in stature," she says. And there are other things to be thankful for. "We had a recent meeting of widows. There were seven of us. Compared to two of the widows who lost both their husbands and their only children, I am lucky. At least I've got a son."

She and Sergei have received financial help from charities, banks and people who read about them on the internet. "An American gentleman sent me money so Sergei could buy a bicycle. A charity paid for us to go on holiday to the Czech Republic. I thought that I was someone who would have been forgotten but it has been quite the opposite. I realised that there are more good people willing to help than bad people."

Still, managing the flashbacks is difficult. A friend of hers took her unthinkingly to the cinema recently and Starkova ran out before the film had started; the site of all those rows of heads in front of her was too awful to bear.

She and Sergei talk often of his sister and father, how funny they were, what made them laugh. The two of them want to travel the world. Starkova looks so glowing, I ask her what moisturiser she uses. She laughs. "Just Russian stuff." And what makes her happy, now? The look of defiance returns. "The birds. The morning. I think life is wonderful."